Many types of industrial, commercial and even residential technical processes and apparatuses have vapor or gaseous flow streams in which liquid particles of various sizes are entrained. In some of these, the presence of the liquid particles negatively affects the apparatus longevity, the apparatus efficiency or possibly even human health.
The following paragraphs describe examples of such systems and such processes where the invention described and claimed herein can profitably be employed.
Air compressed by air compressors and subsequently cooled frequently has water particles entrained with the air. In one application the water particles enter tools causing corrosion and bearing damage. Other applications find the water separating in a compressed air reservoir or tank where the pooled water, if not drained, causes corrosion that weakens the tank walls, leading to potential catastrophic failure.
Refrigeration systems employ compressors lubricated by oils that, in varying amounts are always entrained with the compressed refrigerant discharged by the compressor. The oil lost from the compressor, if not replaced, can lead to compressor destruction from lack of lubrication. The oil conveyed through the system also causes loss of heat transfer capability in both the evaporator and the condenser.
Oil return in miscible oil-refrigerant systems is generally reasonably reliable because the viscosity of oil conveyed within the system has been lowered by a solution of the refrigerant into the miscible oil. By contrast, oil return in systems employing an immiscible oil-refrigerant pair is much less reliable because the solubility of the refrigerant in the oil is slight and therefore the oil retains its original higher viscosity making flow much less certain. While the system piping can be designed to provide sufficiently high vapor velocities to achieve reasonably satisfactory oil flow, there is a penalty of higher gas pressure drop resulting in reduced system efficiencies. In such refrigeration systems employing immiscible refrigerant-lubricant pairs, discharge line oil separators having the highest efficiencies provide a definite advantage. Moreover, drops of liquid refrigerant in the inlet of a refrigerant vapor pump or compressor can cause damage to the compressor. Therefore, such damage must be avoided by preventing liquid drops of a refrigerant from entering into the compressor inlet.
Comfort air conditioning systems lower air temperature and thereby cause moisture condensation. Some of the condensed moisture is carried along with the cooled airstream into the cooled space, thereby causing discomfort, damage to fabrics and furniture and damage to sensitive electronic equipment, where these are located within the cooled space.
To cope with these problems or other problems arising from liquid carry over in vapor streams, many types and designs of mechanical separators have been designed and many are offered commercially for specific uses. The following types are primarily descriptive of those available for use in refrigeration systems to minimize oil carryover in the compressor discharge stream. Some simply reduce the vapor velocity so that liquid particles settle out. Others swirl the gas to provide at least partial centrifugal separation, some provide baffles to secure separation by impingement, some provide fills or meshes which filter or otherwise trap liquid particles on the meshes or in the mesh interstices. However, all these designs have the fault that very small oil particles and liquid droplets escape through the separator and are carried into the refrigeration piping. Further, no special oil separator designs are suggested or provided for immiscible oil-refrigerant systems.
Objectives of this invention are focused on enhancing efficiency of liquid particle separation from a flowing vapor stream using electrical forces alone or a combination of electrical forces and centrifugal forces. The electrical forces are variously known as Electrostatic (ES) when applied to static situations and Electrohydrodynamic (EHD) when applied to situations involving their effects on moving fluids and on the solid and liquid particles carried by such moving fluids.
In accordance with a first objective, the invention provides separation of liquid droplets from a vapor/gas flow (or flow stream) by a system of electrically charged electrodes and electrical fields associated with those electrodes.
In accordance with a second objective, the invention provides a liquid/gas separator in which centrifugal forces are used to concentrate liquid drops close to a collecting electrode.
In accordance with a third objective, the invention provides electrical charging of liquid droplets in a gas flow stream by a first electrode.
In accordance with a fourth objective, the invention provides collection of liquid droplets on the surface of a second electrode within the gas flow stream.
In accordance with a fifth objective, the invention provides separation of liquid droplets from a vapor/gas stream by moving liquid droplets collected on the surface of the second electrode along the surface of the electrode from a region of higher vapor velocity to a region of lower vapor velocity.
Thus, the invention combines a mechanical centrifugal concentration of liquid droplets with electrical separation of said liquid droplets from the gas flow combined with removal of the separated particles from a region of higher vapor velocity to a region of lower vapor velocity, thereby minimizing reentrainment of the removed particles into the flow stream.
In accordance with a sixth objective, the invention provides a device for modifying the initially straight vapor flow into a twisted one in order to subject the liquid particles to a centrifugal force whereby the liquid droplets are concentrated close to the surface of the second collecting electrode.
In accordance with a seventh objective, the invention provides the second collecting electrode with an electrical field or potential of a character designed to attract liquid particles charged by the first electrode.
In accordance with a eighth objective, the invention provides a combination of charging and collecting electrodes in series.
Further objectives include providing a highly efficient device for separating liquid particles from a flowing vapor stream.
Providing such a device that is mechanically simple and easy to fabricate.
Providing such a device that employs means for imparting a high electrical potential or charge of a first polarity to the gas stream and the liquid particles entrained with the gas stream.
Providing such a device where the polarity of the electrical potential is uni-polar, that is non-alternating.
Providing such a device where the potential imparting means is substantially adjacent the device inlet.
To provide such a device having charged means of a second polarity for attracting the particles charged with the first polarity.
To provide such a device where the particle attracting means includes a cylindrical flow means having an electrical potential substantially equal to and of opposite polarity to the potential applied to the particles.
To provide such a device including at least two coaxial spaced apart cylindrical flow means.
To provide such a device including seriatim in the vapor flow stream a first electrode having a first polarity for initially charging liquid particles, a second electrode having a second opposite polarity for collecting some particles, a third electrode for charging remaining particles with the second polarity and a fourth electrode having the first polarity for attracting substantially all the remaining particles.
A device for separating liquid particles from a flowing gas stream, the device comprising seriatim: an inlet for receiving the liquid bearing gas stream, an element positioned in the flow stream bearing a signed electrical charge for charging the gas borne liquid particles, a second element positioned in the flow stream bearing an oppositely signed electric charge for attracting and receiving the liquid particles and conveying said particles out of the gas flow stream.